title: CHK1 levels correlate with sensitization to pemetrexed by CHK1 inhibitors in non-small cell lung cancer cells.
abstract: OBJECTIVE
  Overexpression of checkpoint kinase 1 (CHK1) is associated with poorer patient outcome and therapeutic resistance in multiple tumor models. Inhibition of CHK1 has been proposed as a strategy to increase the effectiveness of chemotherapeutic agents, especially in p53-deficient tumors. In this study, we evaluated the effects of a novel CHK1 inhibitor, MK-8776, in combination with pemetrexed (PMX) on cell proliferation and survival in a panel of p53 mutant non-small cell lung cancer (NSCLC) cell lines.
  
  
  METHODS
  We examined CHK1 expression in 442 resected lung adenocarcinoma specimens using Affymetrix U133A gene expression arrays. We correlated CHK1 mRNA expression with patient survival, tumor differentiation and genomic complexity. We evaluated CHK1 levels in NSCLC cell lines and identified four p53 mutant cell lines with variable CHK1 expression (H1993, H23, H1437 and H1299) based on publicly available gene expression data. We confirmed differential CHK1 mRNA and CHK1 protein levels by qRT-PCR, ELISA, Western Blot analysis (WB) and immunohistochemistry. We examined cell line sensitization to PMX in response to CHK1 inhibition with MK-8776 using WST-1 and clonogenic survival assays.
  
  
  RESULTS
  We found that elevated CHK1 expression in primary lung adenocarcinomas correlates with poor tumor differentiation and significantly worse patient survival. Tumors with elevated CHK1 mRNA levels have a higher number of gene mutations and DNA copy number gain or amplifications. CHK1 inhibition by MK-8776 enhances sensitivity of NSCLC cell lines to PMX. CHK1 mRNA and protein expression are variable among NSCLC cell lines, and cells expressing higher levels of CHK1 protein are more sensitive to the CHK1 inhibition by MK-8776 as compared to low CHK1 expressing cells.
  
  
  CONCLUSIONS
  These findings suggest that CHK1 levels may not only serve as a biomarker of poor prognosis in surgically-resected lung adenocarcinomas, but could also be a predictive marker for CHK1 inhibitor sensitivity, pending in vivo and clinical confirmation.
authors.affiliation: Department of Surgery, Section of Thoracic Surgery, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Grabauskiene
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Bergeron
authors.forename: Guoan
authors.initials: G
authors.lastname: Chen
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Chang
authors.forename: Jules
authors.initials: J
authors.lastname: Lin
authors.forename: Dafydd G
authors.initials: DG
authors.lastname: Thomas
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Giordano
authors.forename: David G
authors.initials: DG
authors.lastname: Beer
authors.forename: Meredith A
authors.initials: MA
authors.lastname: Morgan
authors.forename: Rishindra M
authors.initials: RM
authors.lastname: Reddy
mesh_terms: D000368:Aged; D054316:Biomarkers, Pharmacological; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis* / Q000188:drug therapy* / Q000401:mortality; D000071877:Checkpoint Kinase 1; D017024:Chemotherapy, Adjuvant; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005971:Glutamates / Q000627:therapeutic use*; D006147:Guanine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000188:drug therapy* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D000068437:Pemetrexed; D011379:Prognosis; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011720:Pyrazoles / Q000627:therapeutic use*; D011743:Pyrimidines / Q000627:therapeutic use*; D016019:Survival Analysis; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D054316:Biomarkers, Pharmacological; D004791:Enzyme Inhibitors; D005971:Glutamates; C559815:MK-8776; D011720:Pyrazoles; D011743:Pyrimidines; D016159:Tumor Suppressor Protein p53; D000068437:Pemetrexed; D006147:Guanine; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1
keywords: CHK1; Chemosensitivity; Genomic complexity; LOH; Lung; NSCLC; PMX; Patient survival; RMA; Robust Multi-Array Average; checkpoint kinase 1; loss of heterozygosity; non-small cell lung cancer; pemetrexed